The following discussion of the background of the invention is merely provided to aid the reader in understanding the invention and is not admitted to describe or constitute prior art to the present invention.
Patients with hypertension have some underlying mechanism that elevates their blood pressure. This hypertension can be generally separated into one of two classes: essential hypertension (systemic hypertension of unknown cause); and secondary hypertension (hypertension that results from an underlying, identifiable, often correctable cause). Renal artery stenosis (RAS) is one of the main causes of secondary systemic arterial hypertension. Depending on the severity of the disease, the ultimate clinical consequences (hypertension and renal failure) can lead to mortality at an alarming rate. For example, the reported cumulative two year survival rate for patients diagnosed with unilateral renal artery stenosis is 96%, for bilateral stenosis 74%, and for bilateral stenosis with one or both renal arteries occluded it is 47%. Atherosclerosis accounts for 90% of cases of RAS, and usually involves the ostium and the proximal segment of the main renal artery and the perirenal aorta, with fibromuscular dysplasia accounting for the majority of the remaining cases.
Atherosclerotic RAS is a common and progressive disease. Its prevalence increases with age, particularly in patients who have diabetes, aortoiliac occlusive disease, coronary artery disease or hypertension. Available treatments include percutaneous transluminal angioplasty, endovascular stent placement or surgical revascularization. Doppler ultrasound, magnetic resonance angiography, and computed tomographic angiography has been used to screen for suspected renovascular disease in patients at risk for RAS.